1. Field of the Invention
The present invention relates to, for example, a torsion coil spring used for mobile phones, mobile communication terminal, and the like in which a first housing and a second housing are slidably connected to one another, and to a sliding type mobile terminal equipped with the torsion coil spring.
2. Description of the Related Art
A torsion coil spring having stretching force in the torsional direction has hitherto been used.
For example, in Japanese Unexamined Patent Application Publication No. 2005-174919, a torsion coil spring is used for electronic equipment having a battery pack or a housing part of dry cells. In this electronic equipment, the housing part has a lid for opening and closing an opening of the housing part. The lid is slidably attached to a plate-shaped member. The plate-shaped member is hinge-jointed to a member on a body side fixed to the equipment body, while at the same time constantly biased by an elastic member to a direction of opening the opening. The lid is rendered capable of rotary motion at a position, to which sliding movement is made from a position of closing the opening. The lid further is turned into an open state, where the lid is turned by approximately 90 degrees by the elastic member. While the lid is in the open state, the lid is arranged to abut on the equipment body so that the lid in an upright state.
In a biasing structure using a torsion coil spring disclosed in Japanese Unexamined Patent Application Publication No. 2006-206230, a cylindrical hole where a coil part of the torsion coil spring is housed is provided in an attachment portion to which the torsion coil spring and a member biased by this torsion coil spring are attached so that the coil part is externally supported by the inner wall face of the cylindrical hole. The attachment portion is provided with a hooker on which one end of the torsion coil spring is hooked. The other end of the torsion coil spring is hooked on the biased member.
Further, conventionally, there is a need to make a mobile terminal lightweight and small-sized to secure its portability, while, on the other hand, there is a demand to increase its display part for usability.
A straight type mobile terminal has a limited area that appears on the surface, and the display part and the operation part must be provided on the limited surface, making it impossible to secure sufficient space for the size of the display part. A folding type mobile terminal has the display part on the surface of the first housing and the operation part on the surface of the second housing, the first housing and the second housing being jointed at a hinge part. Consequently, the hinge part occupies much space on the display part, which serves as a hindrance to securing a place for the display part to occupy. Thus, it is occasionally impossible to maximize the size of the display part in the straight type mobile terminal and the folding type mobile terminal.
In view of this, in recent years, a sliding type mobile terminal, in which the display part can be increased, has been proposed. For example, as shown in Japanese Unexamined Patent Application Publication No. 2006-165854, there is known a sliding type mobile phone that includes the first housing having an operation part, the second housing having a display part, and slide engaging means of slidably engaging the first housing and the second housing. This sliding type mobile terminal has a slide resin member on the slide engaging means, and a protrusion is provided on a surface on the side facing the housing that faces the slide resin member, whereby when the both housings are slid in the direction of extension, at the end of the extension where the superposition of the both housings reaches a minimum, the slide resin member is in contact with the protrusion in a compressed state, thus reducing the sound of collision of the stopper at the opening and closing end when sliding for opening or closing.
However, the torsion coil springs disclosed in Japanese Unexamined Patent Application Publication Nos. 2005-174919 and 2006-206230 involve many times of winding to raise the height of the coil part, thereby disabling the springs to be provided in a thin space.
When the torsion coil spring is to be provided in a thin space, winding the coil part into a form of a mosquito-repellent incense, i.e., a series of rings of diminishing diameters on the same plane, is contemplated. In this case, there was such a problem that in order to obtain a necessary biasing power, the outside diameter of the coil part increases and thus takes up much space for installation, making it difficult to provide the spring in an biasing structure of a compact mobile terminal such as a mobile phone.
Further, in a sliding type mobile terminal such as what is shown in Japanese Unexamined Patent Application Publication No. 2006-165854, unless wiring of a signal line (including a flexible substrate) to connect the first housing and the second housing is properly carried out, it may impede sliding operation. As a result, there were problems in which a smooth sliding operation was not possible or the degree of sliding was reduced to prevent the signal line from getting entwined, thus causing the operation part to become small.